Advice on visiting Perth Australia?

I plan on going to Australia soon, Perth specifically. I'm 19 years old and I plan on travelling solo for 2 weeks. I have a debit card and do not have a credit card. These are some questions I have and please tell me if I'm missing anything. Anyone experienced with traveling to Australia solo your advice is greatly appreciated

What do I need to bring with me? (Paperwork, identification, or stuff to allow me to rent a hotel or motel room)

Can I use my California ID to drink at bars or purchase alcohol?

How much money should I bring in USD for the 2 week trip? (I don't plan on doing anything too crazy besides just drinking and relaxing with my friend)

Is it better to get a Bank of America debit card and withdrawal cash at a partner atm or bank?
If not how should I go about exchanging my USD to AUD?

Can I rent a car there? If not, what are some reliable ways of transportation?

Will my t-mobile iPhone work or will I need to be connected to Wi-Fi to make calls?

Feel free to add Any extra information about anything and details about your experience and trip

Why would you want to go there? Really. All the time it takes to fly there, you could enjoy any of the equally beautiful places closer to where you live. I just don't get the appeal of Australia. I really don't. You are from California? Now I really don't understand. There are so many equally beautiful places here and in the west. I don't get it at all.